Dynamic Disks in windows2003

[qshiva]

Dear Members,

Customer wants to use Dynamic Disk so they can extend their volumes without restoring

their data back.

Is there any reason for not changing to dynamic disks ?

What is your experience ?

Its very rare that I have seen customers using dynamic disks ? The data on the file

server is containing office data. So thats not really exiting.

Please can you give me any advise whether I have to change to dynamic yes or no ?

Do I have to stay away from dynamic disks ?

Thanks in advance.

Cheers,

Shiva

[cluberti]

There's nothing wrong with dynamic disks specifically, but there is one drawback - instead of a hardware controller containing the data regarding the array created, the OS partition does. If you lose the OS partition, you lose the arrays it contained as well (well, they can be recovered if you want to take the time and have another machine to use). If you use dynamic disks, just make sure you're VERY careful about the backups you take, both of the data on the dynamic volume, and also of the OS and it's system state data.

[killerb255]

Also, most repartitioning apps are not compatible with Dynamic Disks.

[nmX.Memnoch]

I try to avoid them at all costs too. I prefer to just put a crapload (yes, that's a technical term) of storage space in the server. By the time we get close to filling the space then it's usually time to replace the server anyway.

[jcarle]

Aren't dynamic disks necessary for terabyte volumes?

[cluberti]

Aren't dynamic disks necessary for terabyte volumes?

A basic disk can be 2TB in size - anything larger does need to be dynamic, yes.

[nmX.Memnoch]

Below is the full skinny so no one else has to go searching for the info. cluberti, do you know if this support is going to be included in XP SP3 (and I assume it's already in Vista)?

I've been digging a bit more about the 2TB limit, and found out that they corrected it for Server 2003 SP1.

Windows Support for Logical Units Larger than 2 TB

With Windows Server 2003 Service Pack 1 (SP1) and Windows XP 64-bit Edition (x64), these limits have changed.

Microsoft added support for 64-bit block numbers in the disk/class layer, using the new SCSI Commands included in the SCSI-3 Block Commands-2 command set. Microsoft also enabled GPT support for all Windows Server 2003 SP1 platforms. With this change, for example, a snapshot of a GPT partition on an Itanium-based machine can now be transported to a 32-bit machine for data mining or archiving purposes.

The new limits are as follows:•

Basic or dynamic volume size: 2^64 blocks = 2^73 bytes (too big to pronounce)

•

Maximum NTFS file system size that can be realized on Windows: 256 TB

Note: Disk devices with more than 2 TB of disk space must be converted to GPT format for all of the disk space to be usable. If the device uses MBR format, the disk space beyond 2 TB will be unusable.

http://www.microsoft.com/whdc/device/storage/LUN_SP1.mspx

For those who don't know, GPT stands for GUID Partition Tables. They used to be available only on Itanium based systems, but should now be available for all Server 2003 SP1 and up.

EDIT - Hmm... I just read that an MBR based volume cannot be converted to a GPT volume - it must be wiped clean and started fresh. Maybe I should let my expansion complete... purposefully degrade the array, and use the spare drive to put all the backup data on, then wipe the array and set it to a GPT volume, then copy everything back and expand again. That way I'd have a GPT volume that's ready for future expansions, and this is still when I've got less than a single drive's data on the array (which won't be the case next week...).

Edited August 20, 2007 by nmX.Memnoch

[cluberti]

According to the spec, you need to be able to create a GPT disk, _AND_ your controller must support the SCSI3 9Eh, 88h, 8Ah, 8Fh, and 07h (mostly for SANs with block reassignment capabilities) commands (not all do). Also, according to that page, the controller must support the new disk API and return codes as well - otherwise you'll need to use an MBR disk, which is limited to 2TB for an NTFS volume.

Not to mention, can you imagine what would happen if you needed to run chkdisk on a volume 2TB (or larger) in size? I'd still recommend volume mount points, even if your controller supports GPT disks and you have the disk space to use .

[Zxian]

There's nothing wrong with dynamic disks specifically, but there is one drawback - instead of a hardware controller containing the data regarding the array created, the OS partition does. If you lose the OS partition, you lose the arrays it contained as well (well, they can be recovered if you want to take the time and have another machine to use). If you use dynamic disks, just make sure you're VERY careful about the backups you take, both of the data on the dynamic volume, and also of the OS and it's system state data.

Just a note about this... I recently setup my file server that uses a dynamic GPT disk for the storage array. I read what you said, and realized that I had made a stupid mistake by running the OS drive on a single disk. I went out and bought another disk, and tried to image the original drive, restore it on the RAID1 array, and then repair the installation with the RAID drivers for my system. This didn't work, time and time again, so I ended up having to reinstall the system.

I had backed up all the data on the storage array, so I figured that if the dynamic disk got lost, then it wouldn't be too big of a deal. After Windows was done installing, and I managed to get all the drivers installed, I went back into Disk Management to see where my drives were at. Disk Management reported a "foreign dynamic disk" where the storage array was. I was given the option to import it, and *presto*, all my data is still there.

I suppose what you're trying to get at is that dynamic disk data pertaining to software RAID configurations are highly dependent on the OS. Since my setup is just a simple volume (for the purposes of future expansion), it's probably recoverable in most cases the way I went through it.

[nmX.Memnoch]

According to the spec, you need to be able to create a GPT disk, _AND_ your controller must support the SCSI3 9Eh, 88h, 8Ah, 8Fh, and 07h (mostly for SANs with block reassignment capabilities) commands (not all do). Also, according to that page, the controller must support the new disk API and return codes as well - otherwise you'll need to use an MBR disk, which is limited to 2TB for an NTFS volume.

Quite a few newer SAS controllers have support for >2TB arrays now. 3ware is also making SATA 3Gbps controllers with support for >2TB arrays.

Not to mention, can you imagine what would happen if you needed to run chkdisk on a volume 2TB (or larger) in size? I'd still recommend volume mount points, even if your controller supports GPT disks and you have the disk space to use .

Running it on a 1.8TB array is bad enough!! I only know this because of an issue Dell had with the PE2650 line of servers. If you had multiple controllers there was a timing issue that would cause files to be corrupted on arrays connected to either controller. They finally came out with a BIOS update to correct the issue...but until they did I had to run chkdsk on every array at least once every two weeks...and the particular server in question has one 600GB array, two 1.8TB arrays (7x300GB RAID5 each array) and one 1.9TB array (14x146GB RAID5). Yeah...it took a while. Edited August 21, 2007 by nmX.Memnoch

[killerb255]

Also, you can't boot to a GPT disk without a motherboard with EFI support.

[CorbenDallas]

Don't know if this is of interest but after googling a lot I found this solution to a problem I hade regarding Dynamic disks.

Maybe somebody here wants to know how to revert a dynamic disk back to a basic one.

This info is "stolen" from a forum somewhere, don't know where so if somebody gets mad I guess it has to be erased...

This definately saved my a** one time...

"HOWTO: Convert a dynamic disk back to a basic disk without data loss

**Disclaimer: This ONLY works if you have NOT used ANY of the "new" features of dynamic disks such as extending a partition or software RAID. This is an expert-level procedure, so if you don't know what you are doing, you shouldn't be attempting this.**

1) Install dskprobe.exe on the system. (This is one of the utilities in the Windows 2000 support tools on the install CD, and can be installed by simply copying the .exe file to the hard drive.)

2) Run dskprobe.exe on the system.

3) Select the Drives menu and "Physical Drive. . ."

4) Double click on the drive that you want to convert back to a basic disk. Click the "Set Active" button next to that drive.

5) From the Sectors menu, select "Read"

6) Accept the defaults (begin sector 0, read 1 sector) and click "Read"

7) In the editor, go to the "01C0" line and the third bit should be a "42". Change that to a "07". **Note, a few machines have had this on the "01D0" line instead. I don't know what that means, so I wouldn't try it unless it is on a pure test box. *****

8) From the Sectors menu, select "Write". Confirm all dialog boxes. **Note: This is the step that will hose your box if you have not followed the above instructions correctly.**

9) Exit dskprobe.exe. Reboot

10) Run chkdsk on the affected logical drive(s). If any errors are found, do a chkdsk /f to fix them. Done.

***** svdsinner writes: I did some research, and this relates to having multiple partitions on the drive. I assume partition 1 would be at "01C0", Partition 2 would be at "01D0", Partition 3 would be "01E0", and Partition 4 would be "01F0". I would assume that you would be required to change every partion on the drive back for this to work. However, I have not tested this. Do so at your own risk.

"